The invention relates to an edge trimming system and more particularly to a system for trimming, transporting and chopping scrap from the edge of strip metal.
In a system for manufacturing continuous metal strip, it is important to trim the edges of such strip so that they are clean, burr-free and the strip has a uniform, accurately controlled width. In order to do this, all slack must be taken out of the strip being fed to the edge trimmer system, but the drag or breaking force creating the tension cannot be so great as to hold the material back from free movement through the system. Also, the strip must remain precisely aligned as it passes through the trimmer.
There are many known systems for trimming and chopping scrap from the edges of strip metal. In a majority of these systems, it is difficult to get a precise, burr-free cut because the strip is not securely braced while it is being cut. A few systems concentrate on securing the strip, but there are still problems associated with these securing means. For example, U.S. Pat. No. 2,397,603 discloses the use of a hold-down disk employed to engage the upper surface of the sheet in order to stabilize it. The disk, however, is located inwardly from the cutting blade and therefore the sheet is not stabilized at the point of the cutting. The result is an edge with a burr.
It is very desirable to keep the cutting process moving at an even pace so as to avoid having to shut down the system. Examples of problems which cause the system to be shut down are if the trimmed metal gets tangled in the blades of the edge trimmer or if the trimmed metal escapes before reaching the scrap chopper in which case it must be rethread into a disposal chute.
Several solutions in common use focus on the problem of conducting the cut metal trim away from the blades in order to avoid having to shut down the system. U.S. Pat. No. 2,084,967 discloses the use of a tubular chute inclined downwardly to pass metal trim from an edge trimmer to a scrap chopper. The tubular chute has a rectangular section which receives the scrap. The use of such a rectangular section to receive scrap, however, does not eliminate the problem of scrap catching on an edge of the chute thereby jamminng the chute, nor does such a shape necessarily avoid the problem of scrap "escaping" from the chute. Heretofore, known edge trim disposal systems have not proven to be reliably self-threading when there is a break in the edge trim. Also, no known edge trimmer of this type for metallic strip products has been able to vary the width of the trimmed strip "on the fly".
It is a principal object of the present invention to provide a system for trimming the edges of a moving metal strip that produces a trimmed strip having a very uniform, precise width that can be varied "on the fly".
Another object of the invention is to provide an edge trimming and scrap disposal system where the trimmed edge is self-threading to the scrap disposal system despite breaks in the trimmed edge due to variations in the width of the strip or defects in the strip.
It is a further object of this invention to provide such a system in which the metal strips are trimmed in such a way that the slit edges of the strip have very little burr, even when the metal cut is a soft metal.
It is a still further object of this invention to provide such a system in which adjustments for burr control and for strip width can be made on the fly without shutting down the system.
It is yet a further object of this invention to provide such a system in which the edge trimmed scrap, which may be as narrow as the strip thickness, is chopped into short lengths reliably and automatically.